Today""s electronic products utilize circuits that can perform a variety of applications. Some of the applications include non-volatile semiconductor memory devices as a fundamental building block. The primary mechanism by which data may be stored in non-volatile memory is the memory cell. A typical prior flash memory cell may be comprised of a single Field Effect Transistor (FET) including a select gate, a floating gate, a source and a drain. Information may be stored in the flash cell by altering the amount of charge on the floating gate, which causes the threshold voltage of the flash cell to be varied. A typical prior art flash memory cell may be in one of two possible states, being either xe2x80x9cprogrammedxe2x80x9d or xe2x80x9cerased.xe2x80x9d
According to one prior method, when a flash cell is read, the current conducted by the flash cell may be compared to a current conducted by reference flash cell having a threshold voltage set to a predetermined reference voltage having a value in the separation range. A single comparator may make the comparison and output the result. When a flash cell is selected for reading, a biasing voltage may be applied to the select gate and the same biasing voltage may be applied to the select gate of the reference cell. If the flash cell is programmed, the electrons trapped on the floating gate increase the threshold voltage such that the selected flash cell conducts less drain current than the reference flash cell. If the prior flash cell is erased, little or no excess electrons may be on the floating gate and the flash cell may conduct more drain-source current than the reference cell.
The biasing voltage applied to the select gate in a read operation should be at the proper value in order to determine whether the memory cell is xe2x80x9cprogrammedxe2x80x9d or xe2x80x9cerased.xe2x80x9d0 Thus, there is a continuing need for better ways to supply voltages to the flash memory that allow data to be erased, programmed, or read and allow applications using flash memory to operate properly.